The present invention relates to a needle protection device for a syringe which comprises a needle, a tubular body, to the distal end of which the needle is fixed, and an injection piston which is slidingly arranged in the body, this device comprising a needle protector which is substantially coaxial with the body of the syringe; a protector support which is fixedly joined to the body or which is provided with means for being fixedly joined to the body; a spring which is arranged between and in contact with the support and the protector, the support and the protector being movable relative to each other between a retracted position of the protector, in which the needle of the syringe is disengaged and the spring is locked in a compressed state, and a deployed position of the protector, in which the needle is arranged inside the protector and the spring is, at least partially, relaxed; and means for unlocking the spring.
The invention relates in particular to the field of single-use pre-filled injection syringes which are intended in particular for intramuscular or subcutaneous injections.
These devices are intended to limit to the greatest possible extent the risk, to the user, of accidental pricks after the injection since, once the contents of the syringe have been injected, the needle of the syringe is withdrawn from the patient and the protector is brought into the deployed position all around the needle.
In order to ensure a higher level of safety of use, it has been proposed to provide these devices with resilient means for displacing the protector around the needle of the syringe. In this manner, document U.S. Pat. No. 5,591,138 describes a device of the above-mentioned type which can be used in one of the two following manners: once the injection has been carried out with one hand, the user operates the unlocking means with his other hand in order to disengage the compression spring and to allow the deployment of the protector around the needle. Alternatively, the needle is introduced to a sufficient depth into the skin of the patient to bring about the unlocking of the spring, the spring not being able in any case to relax owing to the protector being pressed against the skin of the patient; in this case, the spring relaxes when the assembly of the device is moved away from the patient.
Therefore, this type of device requires, in order to achieve the desired deployment of the protector, either manipulation with two hands or the protector to be pressed against the skin of the patient. This manipulation ensures neither a high level of ease of use for the practitioner, nor great comfort for the patient. Therefore, these devices remain little used because their use is too far removed from the conventional use of an injection syringe. Furthermore, once the spring is unlocked, the decompression energy of the spring is often violently released without any control by the user being possible, which brings about a degree of instability of the device in the hand of the user. Furthermore, the rigid locking of the protector in the deployed position, in particular in order to prevent any re-use of the device, is possible only by the device being manipulated with two hands.